1. FIELD OF THE INVENTION
The present invention relates to a process for preparing a copper-iron-aluminum catalyst for use in hydrogenation reactions.
2. DESCRIPTION OF THE PRIOR ART
Linear higher alcohols are prepared by reducing methyl esters of fatty acids with high pressure hydrogen at elevated temperatures. Copper-chromium oxide type catalysts, generally called "copper chromite catalysts," are used for this reaction. The original process for the production of catalysts of this type is described in Industrial and Engineering Chemistry, 26, page 878 (1936). No important improvements have previously been made in this basic process. The basic process comprises adding ammonia to a dichromate dissolved in water, adding a cupric salt thereto, filtering the resulting precipitate and then water-washing, drying and calcining the precipitate. In this process, the reaction is incomplete. Therefore, this process involves a serious disadvantage that copper ions and large quantities of hexavalent chromium ions are discharged in the waste water from the filtering and water-washing steps. In order to prevent environmental pollution, these heavy metals should be removed from the waste water by appropriate methods. However, a satisfactory way for finally disposing of the resulting heavy metal sludges has not been found.
In addition to the above disadvantage, the copper chromite catalyst involves another disadvantage which is that, because the particle size thereof is very small, the spent catalyst, after being used for the hydrogenation, cannot be effectively separated from the higher alcohol by filtration unless diatomaceous earth is added thereto as a filter aid. At present, the material that can be used as a filter aid is limited to diatomaceous earth. Because the copper chromite catalyst, after being once used for high pressure hydrogenation, still retains at least 90% of its original catalyst activity, it is desired that the catalyst be used again. However, if the recovered catalyst containing diatomaceous earth is used, the high pressure hydrogenation apparatus wears out rapidly. Thus, the catalyst is usually discarded after only one use. This is quite uneconomical. In addition, it is very expensive to take measures to insure that such spent catalyst does not cause environmental pollution.